Measuring and monitoring pressure is an important diagnostic tool in many medical treatments, especially when treating vascular maladies. For example, aneurysms are often treated by implanting a stent-graft within the aneurysm pocket. Measuring and monitoring blood pressure at the stent-graft can be important in tracking patient health and treatment effectiveness. Pressure sensors within the medical field can be placed in various areas throughout the body, such as within joints, gastrointestinal and spinal locations. The ability to place pressure sensors within industrial applications can also be an effective tool for measuring and monitoring conditions of a process or product.
Various pressure sensors have been used for measuring blood pressure within a vessel or other areas of the body, including capacitive pressure sensors. However, those sensors often require protective casings or inflexible coatings that render the sensors less practical for use with flexible stent-grafts and the minimally invasive insertion techniques typically used with stent-grafts. Such pressure sensors are generally delivered via a catheter directly at the site of the surgery.
The pressure sensors themselves can be formed by metal (e.g., gold or copper) deposition on a polyimide backplane. However, if these sensors are forced into stent-grafts through bending, their inflexible nature will cause the metal and/or polyimide layers to break apart, and eventually these pressure sensors may fail because of fatigue and/or cracking. Furthermore, while some pressure sensors have moved towards using metal traces on a silicone/urethane backplane, such designs are still limited in their flexibility and longevity. For example, typical sensors of this form factor do not lend themselves to be placed within confined areas, flex-endurant areas, or in other such areas where capacitive sensors could be placed if durable enough.
Other pressure sensors omit protective layers entirely, which severely limits the longevity of those pressure sensors. For example, many pressure sensors rely on a flex circuit design not intended for long term implantation.
There is an unmet need to develop a thin, flexible capacitive sensor that can be incorporated into a stent-graft or other forms and can be placed in constrained spaces within the body or industrial applications in which particular temperature, flex, strength requirements are needed.